## DEV Community

Abhishek Chaudhary

Posted on

# Zigzag Conversion

The string `"PAYPALISHIRING"` is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)

P A H N
A P L S I I G
Y I R

And then read line by line: `"PAHNAPLSIIGYIR"`

Write the code that will take a string and make this conversion given a number of rows:

string convert(string s, int numRows);

Example 1:

Input: s = "PAYPALISHIRING", numRows = 3
Output: "PAHNAPLSIIGYIR"

Example 2:

Input: s = "PAYPALISHIRING", numRows = 4
Output: "PINALSIGYAHRPI"
Explanation:
P I N
A L S I G
Y A H R
P I

Example 3:

Input: s = "A", numRows = 1
Output: "A"

Constraints:

• `1 <= s.length <= 1000`
• `s` consists of English letters (lower-case and upper-case), `','` and `'.'`.
• `1 <= numRows <= 1000`

SOLUTION:

``````class Solution:
def convert(self, s: str, numRows: int) -> str:
n = len(s)
if numRows == 1:
return s
op = ""
for i in range(numRows):
curr = i
down = True
while curr < n:
op += s[curr]
if down:
if numRows - i - 1 > 0:
curr += 2 * (numRows - i - 1)
else:
curr += 2 * i
else:
if i > 0:
curr += 2 * i
else:
curr += 2 * (numRows - i - 1)
down = not down
return op
``````